Titanium white (titanium dioxide) powder pigment has good properties including hiding power, tinting strength and opacity, and is able to restrain light, heat and acid-base, so it is used as a kind of white pigment having the best properties, and has been widely used in many fields, such as coatings, fibers, plastics, papermaking, inks With the rapid development of national economy, the demand for titanium white increases continually. The situation of titanium white powder in short supply appears, as a result of that the titanium resources in world are relatively in shortage, and the process for preparing titanium white possesses complex operation, large energy consumption and costly environment protection expense. At the same time, presently most uses of titania is based on its physical and chemical properties of surface, such as higher refractive index, so it is necessary to synthesize a titania composite.
In February, 1999, China Patent CN1206727 disclosed a method of preparing a nanometer composite titanium white, wherein ore powder is used as an inner core, coated with nano ultra-fine TiO2 evenly on the surface to obtain the nanometer composite titanium white. On Apr. 3, 2008, China Patent CN101168838 disclosed a method of preparing a mica titanium material with the following specific steps: dispersing sericite powder evenly in distilled water, putting into water bath at 80° C. to 90° C., dropping TiCL4 solution slowly, adjusting the pH value of the system within a scope of 1.8 to 2.2, and reacting for 2 to 4 hours; then washing with distilled water until the conductivity of filtrate is less than 10MS/S, calcinating at 800° C. to 1000° C. for 0.5-2 hours after drying, and then to obtain the products. On Aug. 20, 2008, China Patent CN101245198 disclosed a type of coated titanium white powder and a preparing method thereof, wherein the coated titanium white powder comprises an inner core and a coating film layer, the inner core is ultra-fine ore powder, and the coating film layer is nano rutile titania; the method of preparing the coated titanium white powder comprises the following specific steps: A. preparing slurry from raw ore powder, B. coating treatment, C. catalyzing the slurry of the coated titanium white powder, D. subjecting the slurry of the coated titanium white powder to a high-temperature heat treatment, E. subjecting the coated titanium white powders to a post treatment.
All the above three types of titanium white powder composites used ore powder as the inner core. The ore powder particle has irregular appearance and coarse particle size a wide range of the particle size distribution, which thus turns out that the titanium white product has irregular appearance, coarse particle size and a wide range of particle size distribution. Moreover, since the titania powder is added into the suspension of ore powder directly, and is coated on the surface of ore powder after dissolving, it can not be ensured that the titania grows on all the surface of ore powder. In addition, the particle size distribution of the titania product is within a wide range, due to that the growth rate of titania can not be controlled. In a word, all the current titania composites have the defects of irregular appearance, coarse particle size and the wide range of particle size distribution, so that limits the applications of titanium white powder in top-grade fields.